Reusable Bending Nail?

[GordonV]

Sorry this post is so long, I blame my profession.

I am new to dedicated grip training as well as the GripBoard. I have not even touched a set of grippers since the late ‘80s. The grippers then were unproductive pieces of junk. After 40 or 50 reps, you could make your hand hurt and forearm burn, but there was no real strength gain. Now, my COCs are in the mail and I am just starting to incorporate grip training into my workouts.

While the above may serve as background, it is not really related to my post. I have been reading various sites on bending with great interest (Bender’s, Duty’s & Black’s to name a few). Is seems like a huge amount of guesswork, trial and error, and shopping to get bending materials. Then once the material has been obtained, it may have to be cut to length, then wrapped and then bent. Once bent it is thrown in a jar or in the trash. The only way to practice bending technique is to bend.

What occurs to me is there is no “gripper” for bending. Is there a reason that a “reusable nail” would not work?

Picture if you will, a gripper but instead of having the handles orientated in a “V” or inverted “V” they would be set on the spring in a straight line. The spring would be in the center and each of the handles would radiate out in a straight line from the center.

HECK, IM or PDA could probably implement this with minimal additional effort. The main wire would need to be bent a bit less to accommodate handle placement. The handles would probably need to be shortened or adjustable to accommodate common bending stock sizes. These “benders” could be made in progression like COC or SOS grippers. Working toward the IM red would probably be much easier if one were able to “standardize” the approach.

Granted the bending practice would not be perfectly transferable because of hand placement (due to the spring) but it seems to make more sense than spending $30 on a box of timber ties for warm-ups.

Any thoughts? Or does this “bender” already exist? I am really good at inventing things that already exist.

[terryduty]

GordonV,

It might interest you to know that a patent has been applied for for an invention designed to increase a steel bender's strength. It is similar in concept to the one that you've proposed. You can get more info on this device by going to the patent office web site: http://gb.espacenet.com/ and entering "EP0095534" into the "View a patent application" field.

Happy bending!

[don of tha new grip]

So is there like a picture of it or somethin?

[porkbone]

There are a few drawings here.

[SqeezeMasterFlash]

It looks interesting, but I think it has the same problems as the idea of putting pieces of pipe over the ends of the nail you're trying to bend. You're developing wrist strength for something alot longer than what you'll eventually be trying to bend.

[RSW]

I am more concerned about all of that energy being stored in the spring as you bend. As the steel bends it deforms and does not spring back. I would imagine that a spring loaded device is going to tend to want to torque around at the end of the bend.

The feel must be very different than a real steel bend. Terry's idea of milling down the center of 7"x5/16" stock looks the most promising to me. That way you would train at bending the same length, but with incrementally increasing bending strengths.

I happen to have purchased a rolling mill recently, which is suitable for cold rolling softer metals. I am considering using Terry's idea with square copper stock, which I can then anneal, straighten and reuse.

Robert

[GordonV]

Thanks for the patent application reference Terry. I had initially thought a similar device using a stacked spring set-up would work, but then I reached the same conclusion as SqueeezeMasterFlash. The distance from the pivot point is so great that performance would be sub optimal.

I was thinking that it would be a single spring, just like a gripper, but it would require two hands to operate. Shorter handles could be used and the diameter of the wire could be varied to bump up resistance.

[Tom Black]

I thought up a similar idea years ago using the same spring as in a torsion spring gripper, basically the handles going in a straight line and the spring in the middle. However, I realized back then that it would not work for long or be safe. Basically, on a torsion spring gripper we are already beyond manufacturer's specs on the deflection of the spring. In the "bending crusher" the deflection would be huge and the spring would break fairly quickly. I think it can even be approximately calculated how many deflections before failure, but suffice it to say not very many. Ideas along the line of the patent may be more fruitful, keep your thinking caps on!

[mcham]

How about making rods out a shape memory alloy? You know the ones that return to their original shape when heated. So you can bend the rod, then put it in hot water to straighten it out again. Trick would be getting the appropriate strength and malleability so that it feels like steel.

[GordonV]

Tom Black raises an excellent point regarding the physical limitations of the material used in present grippers.

I suppose that the easiest way to safely increase the deflection range would be to add more metal to the torsion spring. i.e. make it longer.

Perhaps existing technology could be borrowed from another area. For example, a garage door torsion bar/spring has several revolutions of deflection with a constant level of force exerted on the door. I believe that the life cycle for garage door torsion springs exceeds 10,000 cycles. Granted garage door torsion springs are several feet long, but to accommodate a gripper design with one half a revolution of deflection would require a spring size (in number of coils) about the same size as two gripper springs.

If I am thinking correctly two springs with inverse windings could be used. The springs would be fixed to a bar at the outer ends and mounted to the handles in the middle. The hand placement would be close to the pivot point, so the strength development would be more transferable to actual bending.

I understand that at this point the project becomes somewhat "over engineered" but the number of potential failure points with this design would still be fewer than the European patent that Terry Duty pointed out.

Just something to think about.